1. Field of the Invention
The present invention relates to serial printers which carry out recording by moving a recording head, capable of simultaneously recording a plurality of lines by one movement, in the direction perpendicular to the direction of feeding a record sheet. More particularly, the present invention relates to a serial printer which adjusts record displacement between a recorded row and the next recorded row caused by the movement of the recording head, as well as the adjustment method.
2. Description of the Background Art
A serial printer moves the recording head in the direction perpendicular to the direction of feeding a record sheet, for example, and records one line or a plurality of lines at the same time on the record sheet by the movement. For recording the next line or lines, the record sheet is fed by an amount which corresponds to the recorded line or lines. By repeating the operation, one page of the entire record sheet is recorded which is formed by linking a recorded line to the next recorded line.
For example, the serial printer is a high speed ink jet printer which carries out recording by using a multi-channel head. The ink jet printer emits ink according to image data, fixes the emitted ink particles (droplets) onto a record sheet, and records a reproduced image according to an ink color. In the multi-channel head, a plurality of nozzles which emit ink during one movement are provided in the same direction as the direction of feeding a record sheet. By moving the multi-channel head in the direction perpendicular to the direction of feeding a record sheet, such a number of lines that corresponds to the number of nozzles are simultaneously recorded.
After the multi-channel head is once moved, therefore, the record sheet is fed by an amount which corresponds to the number of line or lines recorded by the multi-channel head. After the record sheet is stopped, the multi-channel head moves again. The operation is repeatedly performed. The feeding, that is, transporting of the record sheet, is carried out while the sheet is held between rollers, for example.
When transporting rollers, for transporting a record sheet, with diameters of 12.00 mm and 12.01 mm are used, recording at a recording density (resolution) of 600 dpi by a multi-channel head with 960 nozzles results in a difference, that is, an error of 1.5 dots between the transport amount of sheets by the transporting rollers with different diameters. Especially for an ink jet printer and the like, it is very difficult to precisely form the transporting rollers or the like, for transporting a record sheet, to have a determined diameter. Therefore, when the transporting rollers or the like are replaced and the replaced transporting rollers are driven at a predetermined transport amount, the above described slight difference in diameter substantially changes the feeding amount and causes record displacement.
FIGS. 1A to 1C are views illustrating recorded states when a multi-channel head carries out recording by moving twice. If the transport amount of a record sheet is larger than a predetermined amount, a white line appears between a previous recorded line and the next recorded line as illustrated in FIG. 1A. If the transport amount of a record sheet is smaller, lines which are recorded by moving the recording head twice are partly overlapped, which results in a thick line as illustrated in FIG. 1B. If recording is carried out at a normal transport amount, a normal record is obtained without any white line or overlapped portion between the record given by the first movement and the record given by the next movement.
As the method of preventing a record failure due to a difference in the transport amount of a record sheet as described above, and especially as the method of adjusting a difference in the transport amount of a record sheet, a technique described, for example, in Japanese Patent Laying-Open No. 8-85242 was proposed. According to the technique, the transport amount of a record sheet is determined by recording a standard pattern on a record sheet, reading the recording result using an image sensor, comparing the read data and the table of the transport amounts of a record sheet which is preset in the apparatus, and calculating an optimum transport amount. Based on the calculation result, the feeding of a record sheet is controlled for subsequent recording.
According the technique described in the above official gazette, if the result which is recorded, for example, by moving the head multiple times is as illustrated in one of FIGS. 1A to 1C, the result is read by an image sensor to determine which state applies to the result. When the recording result illustrated in FIG. 1A, for example, is read by the image sensor, the feeding amount of the record sheet is determined to be excessive, and it is adjusted to be smaller.
According to the technique described in the above official gazette, a standard pattern is actually recorded on a record sheet, the recording result is read by an image sensor, and thus it is recognized easily which state of FIGS. 1A to 1C applies to the actual recorded state. The transport amount of a record sheet can be controlled according to the recognition result. Therefore, it can be controlled so as to record and reproduce the recorded state as illustrated in FIG. 1C.
In this case, it is necessary to provide a multi-head in the serial printer and separately provide an image sensor in the carriage for moving the multi-head. Therefore, the structure for adjusting the transport amount of a record sheet is complicated, and the cost of the serial printer is substantially increased.
Since a light source or the like for illuminating a record sheet is provided together with the above described image sensor in the carriage, the drive load for moving the carriage increases, which results in increase in the burden of a drive motor. Thus, a drive motor which has larger drive torque or the like is required, which leads to the cost increase. Further, a large number of wires such as a wire for the image sensor, a wire for the light source and so on are necessary. The structure for moving and driving the carriage is very complicated.
In adjusting the record displacement described in the above official gazette, only displacement which is caused by the feeding amount of a record sheet can be adjusted, and record displacement in the main scanning direction which is caused by the recording timing of a recording head cannot be addressed.
An object of the present invention is to provide a method of adjusting record displacement of a serial printer which can easily adjust record displacement in the feeding direction of a record sheet and can suppress the cost increase.
Another object of the present invention is to provide a method of adjusting record displacement of a serial printer which can easily adjust record displacement in the main scanning direction of a record sheet and can suppress the cost increase.
Still another object of the present invention is to provide a serial printer which can easily adjust record displacement in the feeding direction of a record sheet and can suppress the cost increase.
Yet another object of the present invention is to provide a serial printer which can easily adjust record displacement in the main scanning direction of a record sheet and can suppress the cost increase.
According to one aspect of the present invention, a method of adjusting record displacement of a serial printer recording a plurality of lines at a time in the main scanning direction includes the steps of recording, in the main scanning direction, a first test pattern formed of a plurality of line patterns spaced apart by a prescribed distance, feeding a record sheet by a prescribed amount, recording a second test pattern formed of prescribed recording patterns, and adjusting the feeding amount of the record sheet based on the positional relations between the first test pattern and the second test pattern.
Since the feeding amount of the record sheet is adjusted based on the positional relations between the first and second test patterns, record displacement in the feeding direction of the record sheet can be adjusted easily, and the cost increase of the serial printer can be suppressed.
According to another aspect of the present invention, a method of adjusting record displacement of a serial printer recording a plurality of lines at a time in the main scanning direction includes the steps of recording, in the feeding direction, a first test pattern formed of a plurality of line patterns spaced apart by a prescribed distance, recording, in the feeding direction, a second test pattern formed of prescribed recording patterns, and adjusting the ink emission timing of a recording head based on the positional relations between the first test pattern and the second test pattern.
Since the ink emission timing of the recording head is adjusted based on the positional relations between the first and second test patterns, record displacement in the main scanning direction of a record sheet can be adjusted easily, and the cost increase of the serial printer can be suppressed.
According to still another aspect of the present invention, a serial printer includes a recording head recording a plurality of lines at a time in the main scanning direction, a first drive unit driving the recording head, a second drive unit transporting a record sheet, a first control unit controlling the first drive unit to cause the recording head to record, in the main scanning direction, a first test pattern formed of a plurality of line patterns spaced apart by a prescribed distance, controlling the second drive unit to feed the record sheet by a prescribed amount, and controlling the first drive unit to cause the recording head to record a second test pattern formed of prescribed recording patterns, and a second control unit controlling the second drive unit to transport the record sheet by a feeding amount determined based on the positional relations between the first test pattern and the second test pattern.
Since the second control unit controls the second drive unit to transport the record sheet by the feeding amount determined based on the positional relations between the first and second test patterns, record displacement in the feeding direction of the record sheet can be adjusted easily, and the cost increase of the serial printer can be suppressed.
According to yet another aspect of the present invention, a serial printer includes a recording head recording a plurality of lines at a time in the main scanning direction, a first drive unit driving the recording head, a second drive unit transporting a record sheet, a first control unit controlling the first drive unit and the second drive unit to cause the recording head to record, in the feeding direction, a first test pattern formed of a plurality of line patterns spaced apart by a prescribed distance, and a second control unit controlling the first drive unit to carry out recording on the record sheet at ink emission timing determined based on the positional relations between the first test pattern and the second test pattern.
Since the second control unit controls the first drive unit to carry out recording on the record sheet at the ink emission timing determined based on the positional relations between the first and second test patterns, record displacement in the main scanning direction of the record sheet can be adjusted easily, and the cost increase of the serial printer can be suppressed.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.